Debit order stop and reversal

I have been calling FNB to stop a debit order going through my account and they keep on saying that the company debiting my account is changing the reference number. So the bank has all power and means to stop any transaction from any customer's account but they cannot stop a debit order. This is so ridiculous, the worst is that every time to call to stop the same debit order they charge you. So they charge for a service they are providing. This is very disappointing. Hence the only way to stop a debit order with FNB bank is to close your bank account. No loyalty to their long term customers at all!